A slightly more concise way to get a lower triangular matrix of 1s: 
use PDL::LinearAlgebra;
sub ltm {
  my ($size, $strictly) = @_;
  my $ltm = ones($size,$size)->tricpy(1);
  $strictly ? $ltm - identity($size) : $ltm;
}

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In reply to Re^2: first stumbling steps in PDL by etj
in thread first stumbling steps in PDL by Discipulus

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